In recent years, digitalization has progressed in the cinema industry, accompanying higher resolution of images and the spread of 3D (three-dimensional; stereoscopic) films. With regard to higher resolution, the spread of what is called 4K images having resolutions of approximately 4000×2000 has progressed.
With regard to 3D images, production techniques have been developed, and films that put less strain on viewers' eyes and allow the viewers to enjoy watching movies for a long time have been released one after another, contributing to increased box-office revenue in the cinema industry.
As techniques for projecting 3D images, some methods, which are described below, have been proposed and put into use.
There is a method in which, by one projector, images for the left and right eyes are switched by time division between polarized light beams orthogonal to each other to be projected, and the images are viewed with glasses that have polarizing filters with planes of polarization orthogonal to each other for the left and right eyes (e.g., see Patent Literature 1).
Note that “polarized light beams orthogonal to each other” mean two linearly polarized light beams whose planes of polarization differ by 90 degrees in some cases, and mean left-handed and right-handed circularly polarized light in other cases. The same applies to the description below.
There is also a method in which two projectors are provided for right-eye images and left-eye images, light beams are projected from the respective projectors as polarized light beams orthogonal to each other, and the images are viewed with glasses that have polarizing filters with planes of polarization orthogonal to each other for the left and right eyes (e.g., see Patent Literature 2).
There is also a method in which an image display part of one light valve is divided into a right-eye image display range and a left-eye image display range, images displayed in these ranges are emitted from a projection lens as polarized light beams orthogonal to each other, and these images are projected to be superimposed on a screen. Also in this method, the images are viewed with glasses that have polarizing filters with planes of polarization orthogonal to each other for the left and right eyes (e.g., see Patent Literature 3).
Furthermore, in order that sufficiently bright 2D (two-dimensional; planar) images and 3D images can be shown even on large screens, projectors of higher output are desired.